Currently, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, and the like are used as commercial secondary batteries. Among them, lithium secondary batteries have little to no memory effect in comparison with nickel-based secondary batteries, and thus lithium secondary batteries are gaining a lot of attention for their advantages of free charging or discharging, low self-discharging, and high energy density.
A lithium secondary battery generally uses lithium oxide and carbonaceous material as a positive electrode active material and negative electrode active material, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate respectively coated with the positive electrode active material and the negative electrode active material are disposed with a separator being interposed between them, and an exterior, namely a battery case, which seals and accommodates the electrode assembly together with an electrolyte.
Generally, a lithium secondary battery may be classified into a can-type secondary battery where the electrode assembly is included in a metal can and a pouch-type battery where the electrode assembly is included in a laminate sheet pouch of aluminum and polymer resin, depending on the shape of the exterior.
Recently, secondary batteries are widely used not only for small-sized devices such as cellular phones but also middle-sized or large-sized devices such as vehicles and power storages. When being used for middle-sized or large-sized devices, a great number of secondary batteries are electrically connected to enhance capacity and output. In particular, the pouch-type secondary batteries are frequently used for the middle-sized or large-sized devices due to small weight, low production costs and easy shape change.
However, the pouch-type secondary battery is generally not easily stacked since it does not have large mechanical rigidity and does not have a structure for coupling batteries to each other. Therefore, when a battery module including a plurality of pouch-type secondary batteries is constructed, a separate coupling member such as a cartridge is required to protect the secondary battery stack against external impacts, prevent movements thereof and allow easy stacking.
In an existing technique, when a battery module is configured, an overlap design is applied to the secondary battery body, or a surface pressure is applied to a large area portion of the body in order to fix secondary batteries. If the existing battery module configuration is used, when an external vibration is applied, the body portions of the secondary batteries are shaken, and also the mechanical impact is transmitted to an electrode tab drawn from the electrode assembly and an electrode lead connected thereto, thereby causing a problem in the electric connection. As described above, the existing battery module configuration has a defect in view of electrode lead protection.